Production of aromatics from petroleum



Patented Sept. 22, 1953 UNITED STATES PATENT OFFICE PRODUCTION OF AROMATCS FROM PETROLEUNI Application May 10, 1950, Serial No. 161,212

6 Claims. (Cl. 260-672) My invention relates to the production of naphthalene in substantial yields from hydrocarbon fractions rich in alkylated fused-ring aromatics, especially petroleum cycle stocks, by conversion ih the presence of a water gas-active, steam insensitive catalyst, hydrogen and steam.

Conventional cracking operations to prepare petroleum products such as gasoline from heavier hydrocarbon fractions is essentially an incomplete process when the total conversion to useful products is considered. In particular, cycle stock, or relatively refractory hydrocarbons boiling in the gas oil range accumulates in vast quantities. As a result, a diflicult problem is presented in handling these cycle stocks to further improve the commercial aspects of cracking operations. Continued recycling of such fractions in the system for additional conversion becomes 'uneconomical because of their general refractory character. On the other hand, as useful products cycle stocks have extremely limited utility. For instance, as heating oils these hyd rocarbons have low or negligible Values while their ignition quality is too poor for practical use as diesel fuels.

Cycle stocks are characterized by a high content of alkylated fused-ring aromatic compounds, particularly alkylated naphthalenes such as the methyl naphthalenes. Although these materials have limited present market value and cannot be individually separated, naphthalene itself has a denite market value if prepared at low cost,

I have found that naphthalene can be prepared at low cost, eiciently and in substantial yield from hydrocarbon fractions rich in alkylated fused-ring aromatics, particularly cycle stocks from cracking operations, by conversion in the presence of a water gas-active, steam-insensitive catalyst, hydrogen and steam. I have found that reaction conditions areA important to the practice of my invention. Essentially, I react the aromatic-rich fraction with hydrogen and steam at a temperature in the range approximating 1200 to 1800.l'.V The hydrocarbon feed is introduced at a liquid space velocity between about 0.1 to 5.0 volumes per volume of catalyst per hour.` The hydrogen and steam is present in the reaction in the amount of about 1 to 20 moles of each for each mole of the hydrocarbon feed, the hydrogen present being rcalculated as pure H2 and the steam as water. Although the pressure reaction conditions offer considerable latitude, I use pressures from about atmospheric to 100 p. s. i., which are particularly attractive from a commercial and economic aspect. The catalyst employed should be insensitive to steam, have water gas activity, and Dis one which will promote hydrodealkylation, for instance, a potassium promoted iron oXide-chromia catalyst.

By Way of example, I particularly contemplate introducing a cycle stock from a conventional cracking operation, rich in alkylated fused-ring aromatics and boiling in the range 400-600 F., into a reaction zone into which is also passed substantially pure hydrogen, or a gas containing a large proportion of hydrogen, and superheated steam. Advantageously, the hydrogen is present as a mixture of the fixed or tail gases from the process itself augmented when necessary by the addition of pure hydrogen. The hydrogen gas (considered as pure hydrogen) to hydrocarbon feed molar ratio is preferably between about 4 to 10, while the steam (considered as water) to oil ratio is advantageously in the same range. A steam insensitive, water gas active catalyst is present in the reaction zone, say a potassium promoted iron oxide-chromia catalyst. The reaction is carried out at a temperature of about 1400 F., at a pressure of about 30 to 40 p. s. i. g., with a hydrocarbon feed space velocity between 0.1 to 1.0. The catalyst may be cleaned whenever necessary by passing steam through it when the system is off-stream. The effluent products from the reaction zone are then fractionated to separate the naphthalene and other useful aromatic products, e. g. benzene, toluene and xylenes. Alkylated fused-ring aromatic compounds, such as methy1 naphthalenes, `and other heavier unconverted fractions boiling above naphthalene removed from the reaction products may be cycled back to the reaction step along with the tail or xed gases.

Although the process according to my invention is especially adaptable to petroleum cycle stocks, which are readily available at low cost and in considerable quantities, other sources of alkylated fused-ring aromatics may be employed. In general, these cycle oils and other similar fractions contain large proportions of compounds with polycyclic aromatic nuclei attached to which are such groups as methyl, ethyl, propyl (or higher) radicals as well as cycloalkyl, e. g., cycloheXyl, and aryl radicals. In particular, I contemplate using hydrocarbon fractions essentially consisting of alkyl, polyalkyl, aryl or polyaryl naphthalene derivatives or any oil containing these derivatives in appreciable amounts. I especially prefer cycle stocks derived from cracking operations such as those boiling in the range of 400 to 600 F. Coal tar fractions of similar boiling ranges can also be used. However, certain other heavier fractions rich in alkylated fused-ringaromatics such as derivatives of anthracene and phenanthrene are useful. Pure or highly concentrated naphthalene derivatives are not essential since any non-aromatic constituents in the charge will be hydrocracked to lower boiling hydrocarbon liquids :and gases from which the naphthalene is removed by distillation. In addition, the presence of non-aromatics and alkylbenzenes in the feed result in the production of benzene, toluene and xylenes, as well as useful hydrocarbon gases, particularly butane. Cycle oils of relatively loW aromatic concentra.- tion may be initially treated or prepared prior to reaction. For example, solvent extraction with a selective solvent of the nature of furfural or sulfur dioxide will effect separation from nonaromatic constituents present in undesirable amounts. o

I have found that the use of a catalyst in my process that is substantially insensitive to steam, that haswater gas activity and that promotes hydrodealkylation will substantially improve-the yield of naphthalene. The catalyst must be stable in the presence of steam. It must be able to liberate hydrogen from the steam by the water gas reaction and promote hydrodealkylation, while at the same time not catalyzing or promoting, other than to a very limited degree, competing reactions such as cracking and aromatic condensation. Included in this group of catalysts are potassium promoted iron oxide-chromia (e. g. 88% Fe2O3, 5% Cr203, 7% KzCOg); Vnickel-calcium phosphate mixtures promoted with chromia (e. g., 30.5% Ca, 5.1% Ni, 1.3% CrzOs); promoted iron-magnesia (e.l g., 16A to 19% FezOa, 3.5 to 4.5

CuO, 62 to 75% MgO, 4 to 6% KzO) sodium promoted iron oxide-chromia (e. g., 90% Fe203, 6% CrzOs, 4% NazCOs) sodium hydroxide promoted activated charcoal (e. g., coconut shell activated carbon impregnated with 3 to 4% NaOH); barium, potassium, `or strontium promoted coke or charcoal stabilized with copper oxide, and silicamagnesia promoted withV an alkali `metal and stabilized with cop-per oxide. I believe, although my invention is not predicated upon-any particu-4 lar theory, that the sodium, potassium., barium and-strontium components, for instance, of these illustrative catalysts serve to promote the water gas reaction While the other constituents of the catalysts apparently promote formation of the naphthalene and other useful compounds as well as improving catalyst life.

I add steam, advantageously superh-eated, to the reaction mixture undergoing conversion in the amount of at least one mole (considered as Water) of steam for each mole of oil feed, to 20 moles of steam per mole of oil. An amount less than one moleY is relatively ineffective while quantities in excess of 20 moles are wasteful andl do not appreciably improve the reaction. I prefer to add steam in the molar ratio of about 4 to l0. The steam serves, in large measure, to make available in situ hydrogen, by thewater gas reaction, thereby maintaining catalyst activity by4 the removal of carbonaceous deposits on the catalyst. The hydrogen s o. produced is utilized inr the dealkylation reaction and prevents excessive tar formation (i. e., less aromatic compound condensation) and also reduces coke formation by preventing cracking of the feedstockto coke and gas.

Although it is not necessary to employ pure hydrogen in my process, I prefer to use hydrogen in the highest concentration that is economically feasible. However, mixtures of hydrogen with other gases or compounds which decompose orl react so as to make available hydrogen in situ 4 can be used. I particularly contemplate using, for economic reasons, the non-condensible or tail gases from the efliuent products of the reaction which are rich in hydrogen and which may be augmented when necessary by adding' substantially pure hydrogen so that hydrogen is maintained in excess during the reaction at all stages Yof contact. However, steam alone (no free hydrogen atV all), although it will be decomposed to make available some hydrogen, is not satisfactory. Diluent gases other than hydrogen, such as nitrogenfor propane, are also not satisfactory since their use tends to appreciably lower yields and coke formation. I use about 1 to 20 moles of the hydrogen gas, calculated as pure H2, foreach mole of the hydrocarbon feed, and prefer a molar ratio of about 4 to 10. At least one mole of hydrogen is needed to prepare naphthalene in attractive yield, while using hydrogen'in amounts above the upper limit is essentially wasteful.

The reaction isf carried out at a temperature in the' range approximating 1200 to 1800 F. Below thev lower limit of 1200 F. the yield of naphthalene is unattractive, while thermal environments exceeding about 1800" F. are difficult to attain and are impracticable becausey of present day equipment'limitations. The pressure conditions may be varied Widely, although for economic reasons I prefer relatively low pressures inthe rangeA approximating about 0 to 100- p. s. i. g. I have found that reaction temperatures of about 1400 to 1450 F. for a pressure of about 30 to 40 p. s. i. g. are particularly advantageous.

rlhe hydrocarbonfeed is introduced into the reaction Vat. a liquid space velocity in the range approximating 0.1 .to 5.0 volumes per volume of catalystY perhour. Although it is evident that there is considerable latitude in the rate of oil introduced', at temperatures between about 1200 to i450 F., the space velocity is preferably be low about 1.0.

The eiiluentfproducts from the hydrodealkylation of the alkylated fused-ring aromatics formed in the process according t-o my invention are fractionated tor yield chiefly naphthalene of good commercial grade. For instance, naphthalene of about purity obtained from a 400-600 F'. boiling range cycle oil is readily marketable, while even redistillation to a premium product of upwards of purity is usually warranted. The effluent from conversions at a 1500 F. or higher temperature usually contains naphthalene in extremely high purity while the eluent from lower temperature reactions may require work up, say by solvent extraction, to prepare a more useful product. Besides naphthalene, other valuable dealkylated aromatics result from the conversion reaction,` such as high octane gasoline, which have additional utility.

The following examples are intended to more clearly illustrate my invention.

Example I A hydrocarbon fraction consisting essentially of methylnaphthalenes was introduced into a reactor vessel at the liquid space velocity of 0.39V

volume per volume of catalyst per hour. The reaction vessel was packed with a steam-insensitive, Water gas-active catalyst material havin the following composition by weight: Y

A hydrogen-rich gas mixture 'was introduced into the same reactor containing, for each mole of feed introduced, 4 moles of hydrogen and 10 moles of steam (as water) 4The mixture was reacted at a temperature reaching a peak of 140 0 F. for 4 hours, at 30 p. s. i. g. pressure. The effluent products from the reactor had the following composition by weight as based on the feed:

Per cent Liquid 84.3 Gas 5.0 Coke 0.6 Loss 10.1

The analysis of the effluent gases by mole percentage was:

Per cent Hydrogen 88.4 Carbon dioxide 3.6 Methane 2.9 Other gases 5.1

The liquid products were distilled into the following fractions by weight:

Per cent 440-460 F 30.2 460-480 F 46.6 Bottoms 21.6

These liquid products analyzed as follows, by Weight on the charge:

, Per cent Naphthalene 19.0 Methylnaphthalene 43.7

The ultimate naphthalene yield was 33.8%.

Emample II A hydrocarbon fraction consisting essentially of methylnaphthalenes was introduced into a reactor vessel at the liquid space velocity of 0.23 v./v./hr. The reaction vessel was packed with a steam-insensitive water gas-active catalyst material having the following composition by weight:

Per cent F8203 88 CI2O3 5 KzCOs 7 Per cent Liquid 91.5 Gas 7.5 Coke 1 .0 Loss 0.0

The analysis of the eiiluent gases by mole percentage was:

Per cent Hydrogen 74.9 Carbon monoxide 7.3 Carbon dioxide 8.1 Methane 6.9 Other gases 2.8

The liquid products were distilled into the following fractions by weight:

Per cent 400460 F 48.9 460-480 F 30.4 Bottoms 15.6

These liquid products analyzed as follows by weight on the charge:

Per cent Naphthalene 39.5 Methylnaphthalene 31.1 The ultimate naphthalene yield was 57.4%.

Example III A hydrocarbon fraction consisting essentially of methylnapthalene was introduced into a reactor vessel at the liquid space velocity of 0.18 v./v./hr. The reaction vessel was packed as a bed with a steam-insensitive water gas-active catalyst material having the following composition by weight:

Per cent F8203 88 CrzOs 5 K2CO3 '7 A hydrogen-rich gas mixture was introduced into the same reactor containing, for each mole of feed introduced, 4 moles of hydrogen and 10 moles of steam (as water). The mixture was reacted -at a temperature reaching a peak of 1400 F. for 5 hours, at 30 p. s. i. g. pressure. The efuent products from the reactor had the following composition by weight as based on the feed:

Per cent Liquid 85.1 Gas 13.9 Coke- 0.5 Loss 0.5

The analysis of the effluent gases bymole percentage was:

Per cent Hydrogen 70.0 Carbon monoxide 7.6 Carbon dioxide 15.5 Methane 5.1 Other gases 1.8

The liquid products were distilled into the following fractions by weight:

Per cent 400460 F 37.3 460-480 F 49.7 Bottoms 7.7

These liquid products analyzed as follows by weight on the charge:

Per cent Naphthalene 33.2 Methylnaphthalene 39.1

'If'he ultimate naphthalene yield was 54.5%.

Example IV A hydrocarbon fraction consisting essentially of methylnaphthalene was introduced into a reactor vessel at the liquid space velocity of.0.18 v./v./hr. The reaction vessel was packed with a steam-insensitive water gas active catalyst material having the following composition by weight.

Per cent FezOs 88 C120s 5 KzCOts 7` 7. Only steam was introduced into the' same re#- actor at the rate of moles-of steam (as water) for each mole of the feed introduced. The mix ture Was reacted at a temperature'reaching a peak of 1400 F. for 5 hours, at atmospheric pressure. The eluent products from the reactor had the following composition by weight as based on the feed: Per cent.

Liquid 73.01 Coke 1.6

The liquid products were distilled into the following fractions by weight:

Per cent I. B. P.400 F 1.1 400-460 F 11.0 460-480 F 7.2 Bottoms 72.5I

The liquid products were analyzed and only 3% were recovered as naphthalene, indicating that steam alone is relatively ineffective.

y Example V A hydrocarbon fraction. having the following analysis:

ASTM I. B. P., F 452 ASTM E. P., F 497 API gravity, 14.7 Olens, per cent wt 4.3i Aromatics, per cent wt 86.7

Naphthalene, per cent wt 0.7'

Methylnaphthalenes, per cent wt 51.6

- Per cent Gas (C3-, Hz, C as oxides) 25.0 Gasoline (410 F.E. P.) 3.0 Naphthalene 7.8 Methylnaphthalene 15.9 Other liquid products 47.8 Coke 0.5

The hydrogen consumption was 3110 cubic feet (at S. T. P.) per barrel of feed oil. Thus without the use of a steam-insensitive catalyst with water gas activity the yield of naphthalene was only 7.8%. Y

Example VI A hydrocarbon fraction having the following analysis:

AST'lVI I. B. P., c'F

ASTM E. P., F 497 API gravity, 14.7 Olefins, per cent Wt 4.3 Aromatics, per cent wt 86.7 Methylnaphthalenes, per cent wt 51.6 Naphthalene, per cent wt 0.7

was introduced into-a reactor vessel at the liquid space velocity of 0.23 v./V./hr. The reaction vessel was packedwith a steam-insensitive, water "gas-active catalyst material having the following .composition by weight:

Per cent F6203 88 CIzOa 5 K2CO`3 7 .A gas mixture of steam and hydrogen was introduced into the same reactor in the molar ratio lof 16 moles of steam and 5 moles of hydrogen for each mole of hydrocarbon feed. The Ymixture was reacted at a temperature reaching a peak of 1350 F. at 30 p. s. i. g. pressure. The reaction products had the following composition by weight as based on the feed:

l Per cent Gas (Ca-, H2, C as oxides) 32.1 Gasoline (410 F.-E. P.) 2.6 Naphthalene 13.2 Methylnaphthalene 23.1 Other liquid products 29.0

The hydrogen make,v considered on a oncethrough basis, was 5550 cubic feet (at S. 1"` P.) per barrel of feed oil.

Example VII A hydrocarbon fraction having the following analysis;

ASTM I. B'. P., "F

ASTM E. P., F 497 API gravity, 14.7 Olens, per cent Wt 4.3 Aromatics, per cent wt 86.7 Methylnaphthalenes, percent wt 51.6 Naphthalene, per cent wt 0.7

was introduced into a reactor vessel at the liquid space velocity of 0.20 v./v./hr. The reaction vessel was packed with a steam-insensitive, water gas-active catalyst material having the following composition by weight:

Per cent F8203 90 Cr203 6 NazCOo 4 A gas mixture of steam and hydrogen was introduced into the same reactor in the molar ratio of 24 moles of steam and 18 moles of hydrogen foreach-mole of hydrocarbon feed. The mixture was reacted at a temperature reaching a peak of 1350 F. at 40 p. s. i. g. pressure. The reaction products had the following composition by weight based on the feed:

Per cent Gas (C3, H2, C as oxides) 42.0 Gasoline (410 F.E. P.) 1.3 Naphthalene 17.7 Methylnaphthalene 14.0 Other liquid products 25.0

The hydrogen make, considered on a oncethrough. basis, was 6550 cubic feet per barrel of feed oil. Hence by the use of a steam-insensitive catalyst with water gas activity the naphthalene yield is as high as 17.7 wt. per cent, compared to 7.8 Wt. per cent of Example V in Which no such catalyst material was used. Furthermore, coke formed during the process is continuously removed by the water-gas reaction and the operation is self-sustaining in hydrogen.

The accompanying drawingis a flow diagram illustrating somewhat schematically a continuous process according to my invention.

A petroleum fraction rich in alkylated fusedring aromatics, acycle oil Vboiling in the range esente 9- 400-600 F. from-a cracking operation, is introduced by line I. Extraction zone 2 is provided, accessible by line 3, if it is necessary to improve the quality of the feed oil to be treated by removing non-aromatics with a selective solvent such as furfural or sulfur dioxide. In any event, the feed oil is passed by line I through heat zone d, while the hydrogen gases passing to the reaction are also heated in this zone by passing through line 5. The hydrogen gases comprise substantially the hydrogen-rich tail gases separated from the reaction products. Both the feed oil and hy- -drogen gases are then heated to an elevated temperature in this heat zone 4, for instance about 500 to 700 F., and mixed together when they are passed by single line 'I to the reaction zone. Superheated steam is added by line 8 to the mixture entering the reaction zone 9. Reaction zone S is packed with a catalyst material insensitive to steam and which has water-gas activity. Advantageously, the catalyst is a sodium promoted iron oxide-chromia mixture, for instance, by weight, 90% Fe2O3, 4% K2CO3 and 6% CrzOa. The reaction is carried out at a temperature in the range approximating 1200" `to 1800 F. at a pressure, although considerable latitude is afforded, advantageously in the range of atmospheric to about 100 p. s. i. g. Preferably, the reaction is carried out at a temperature of about 1400o F. at about 30 to 40 p. s. i. g. The hydrogen gas feed, steam and charge oil introduced into the reactor are regulated so that a molar ratio of hydrogen to oil of 1 to 20 and of steam to oil of 1 to 20 exists, calculated as pure hydrogen and as water. The hydrocarbon is fed into the reaction zone at a liquid space velocity of 0.1 to 5.0 volumes per volume of catalyst per hour, advantageously 0.1 to 1.0 when temperatures below 1500P F. are employed. A water quench I is provided in the reaction zone so that thermal conditions may be regulated during reaction and for cooling of the hot effluent vapors. The eluent products from the reaction are taken off by line II and passed through cooling zone I2, advantageously a waste heat boiler where they are cooled to about 300 to 400 F. The products are then passed through liquid separation zone I2d, a knockout drum, where the non-condensible gases are separated from the liquid by line I3. The xed or non-condensible gases are then passed by line VI3 to a second liquid separation means ill, another knockout drum, where any remaining liquid is removed. The non-condensible or tail gases, rich in hydrogen, are then cooled in cooling zone I5 and passed to carbon dioxide scrubber I6 by line I'I. Any amount of the gases may be bled out by line I8. After the CO2 has been removed these gases are recycled back to the reaction as desired. The liquid separated out by the knockout drums passes to water separator 23 by lines 2i and 22, although the liquid from the rst drum may be additionally cooled in cooling zone so that it is at a temperature between about 90 to 120 F. The water is then removed from the products by line 2d. The liquid is then heated again in heating zone 25 and is introduced into fractionating zone 2l for separation into useful constituents by line 26. From the fractionating zone 21, the gasolinerange boiling constituents are removed as overhead by line 28, tar as bottoms by line 29, a crude methylnaphthalene fraction by line and a crude naphthalene fraction by line 3 I. The gasoline and naphthalene fractions are passed to storage or may be redstilled for additional purity. Crude methylnaphthalene and the bottoms may be recycled as desired by line 32 to be adrnixed with the feed stock.

I claim:

1. The method of converting higher molecular weight hydrocarbons fractions rich in alkylated fused-ring aromatic compounds to lower molecular weight hydrocarbons which comprises passing the hydrocarbon fraction into a reaction zone in the presence ofa hydrogen-rich gas, steam and a catalyst prepared by combining a major amount or iron oxide with promoting amounts of chromia and a member selected from the group consisting of inorganic, oxygen-containing sodium and potassium compounds which aord their respective oxides under the reaction conditions and which is steam-insensitive, water gas-active and which promotes hydrodealkylation, at a liquid space velocity in the range approximating 0.1 to 5.0 volumes per volume of catalyst per hour, the hydrogen and steam each belng present in the reaction in the amount of about l to 20 moles of each for each mole of the hydrocarbon fraction, maintaining the reaction zone at a temperature in the range approximating 1200 to 1500u F., and separating the lower molecular weight hydrocarbons from the eiuent reaction products.

2. The method according to claim l wherein the reaction is carried out at a pressure in the range approximating 0 to 100 p. s. i. g.

3. The method according to claim l wherein the hydrogen-rich tail gases are separated from the eifiuent reaction products and are recycled to the reaction zone.

e. 'l-he method according to claim 1 wherein the hydrogen-rich tail gases and hydrocarbons boiling above naphthalene are separated from the eiiluent reaction products and are recycled to the reaction Zone.

5. The method of preparing naphthalene from petroleum cycle stocks rich in alkylated naphthalenes which comprises passing the cycle stock into a reaction zone in the presence or a hydrogen-rich gas, superheated steam and a catalyst prepared by combining a major amount of iron oxide with promoting amounts of chromia and a member selected from the group consisting or" inorganic, oxygen-containing sodium and potassium compounds which afford their respective oxides under the reaction conditions and which is steam-insensitive, water gas-active and which promotes hydrodealkylation at a liquid space velocity in the range approximating 0.1 to 5.0 volumes per volume of catalyst per hour, the hydrogen and steam each being present in the reaction in the amount of about 1 to 20 moles of each for each mole of the petroleum fraction, maintaining the reaction zone at a temperature in the range approximating 1200 to 1800 F., separating the tail gases from the effluent reaction products and recycling said gases to the reaction zone, and fractionally distilling the liquid reaction products to separate therefrom naphthalene.

6. The method of preparing naphthalene from alkylated naphthalenes which comprises passing the alkylated naphthalene into a reaction zone in the presence of a hydrogen-rich gas, steam and a catalyst prepared by combining a major amount of iron oxide with promoting amounts of chromia and a member selected from the group consisting of inorganic, oxygen-containing sodium and potassium compounds which afford their respective oxides under the reaction conditions and which .ascia-17e is steam insensitive, Watergas-active yand which promotes hydrodealkylation at a .liquid 'space velocity in 'the range approximating 0.1 1105.0 volumes per Volume of catalyst per hour, the hydrogen and steam each being present in the reaction in the :amount of about 1 `'to .20 moles of each 'for each mole of 'the valkylate. naphthalenes, maintaining the reactionzone at a temperature in the range approximating "1200'o to 1800 1F., separating the tail gases fro'm the eiiiuent reaction products and recycling said gases to the eaction zone, and fractionally dstlling the liquid reaction pro'dcts t separate therefrom naphthalene. Y Y

LA 'VERN H. BECMKBERGER.

References Cited .in lthe Yle of this patent UNITED 'STATES PATENTS Number n .Name Date Ramage Jan. 18, 1921 Sweeney July 25, 1939 Sachanen et a1. Mar. 19, 1940 Asbury Dec. 2, 1941 Eggeist'n etal. Jan. 21, 1947 Karby Sept. 2, 1947 Haense1 Mar. v2, 1948 

1. THE METHOD OF COVERTING HIGHER MOLECULAR WEIGHT HYDROCARBONS FRACTIONS RICH IN ALKYLATED FUSED-RING AROMATIC COMPOUNDS TO LOWER MOLECULAR WEIGHT HYDROCARBONS WHICH COMPRISES PASSING THE HYDROCARBON FRACTION INTO A REACTION ZONE IN THE PRESENCE OF A HYDROGEN-RICH GAS, STEAM AND A CATALYST PREPARED BY COMBINING A MAJOR AMOUNT OF IRON OXIDE WITH PROMOTING AMOUNTS OF CHROMIA AND A MEMBER SELECTED FROM THE GROUP CONSISTING OF INORGANIC, OXYGEN-CONTAINING SODIUM AND POTASSIUM COMPOUNDS WHICH AFFORD THEIR RESPECTIVE OXIDES UNDER THE REACTION CONDITIONS AND WHICH IS STEAM-INSENSITIVE, WATER GAS-ACTIVE AND WHICH PROMOTES HYDRODEALKYLATION, AT A LIQUID SPACE VELOCITY IN THE RANGE APPROXIMATING 0.1 TO 5.0 VOLUMES PER VOLUME OF CATALYST PER HOUR, THE HYDROGEN AND STEAM EACH BEING PRESENT IN THE REACTION IN THE AMOUNT OF ABOUT 1 TO 20 MOLES OF EACH FOR EACH MOLE OF THE HYDROCARBON FRACTION, MAINTAINING THE REACTION ZONE AT A TEMPERATURE IN THE RANGE APPPROXIMATING 1200* TO 1800* C, AND SEPARATING THE LOWER MOLECULAR WEIGHT HYDROCARBONS FROM THE EFFLUENT REACTION PRODUCTS. 